Analog tool for a digital world

A brief intro to Ansel Adams Zone method

Tribute to Ansel Adams. Photo by Mark Abouzeid.
Tribute to Ansel Adams. Photo by Mark Abouzeid.

This article is a response to recent inquiries on the use of Ansel Adams Zone system in digital photography and video. It is for professionals who understand histograms, tonal matching and manual exposure.

Consider the work of Ansel Adams and the technology with which he had to create: No light meters to measure exposure, no colour cards to set white balance, no polaroids to test shoot, no histogram to set tonal range, and each shot cost a considerable amount. Add to this particular physical constraints: a large wooden box weighing several kilos, shutter speed set by pressing and then releasing a plunger, one lens with one variable for depth of field (f-stop), film plates that could only register six stops of luminosity and no way to increase the sensitivity without changing film.

How is it possible, then, that his landscapes are the standard by which many photographers measure their skill and eye. “Necessity is the mother of invention.” His zone system was the key. Today, thanks to histograms and exposure meters, the zone system is an invaluable tool for digital professionals.

The zone method, appropriately used, provides digital photographers with complete creative control over exposure, luminosity, and tonal range before the shot and in post-production. There is one caveat, however: it is virtually useless if manual exposure control is non-existent; or if uncompressed data (raw) is unavailable.

So, if you are shooting in automatic or saving in jpeg, stop reading now. Raw files contain all the information a camera can record, despite not displaying it. Raw files hold up to 11 stops of dynamic range compared to 7 in jpeg. By making changes to parameters in raw files, we can use the hidden data. Most raw files capture and record one more stop of information in the blacks and two more stops in the whites allowing us to ‘save’ overexposed or underexposed photos.

Jpeg or other forms of lossy compression abandon all information not referenced in the image. You can adjust exposure, tonal and luminous ranges but nothing truly changes: the data no longer exists. Changing a jpeg file to tif, changes nothing, the information doesn’t exist.

Why do we use the Zone Method in Still Photography or Video Production?

  1. Exposing the image the way you see it, not the camera;
  2. Proper dynamic range in an unbalanced scene (snowfield)
  3. Getting skin tone right in camera;
  4. Compressing or expanding the dynamic range to emphasise contrast or subtlety, 2D or 3D; and
  5. Creative shooting and post-production mixing techniques (high key, low key).

It can be used to various degrees depending on the scope of the photo and experience of the photographer:

  1. Single point subject exposure,
  2. 2 point dynamic range, and
  3. 3 point complete creative control.

However, while the latter two can be used by beginners, the former is dangerous unless applied by an expert. Single point exposure requires the photographer to have learned the zonal values of hundreds of real-world objects. For example, setting appropriate skin tones can be difficult if you don’t know within what zone Caucasian, African or Asian skin falls. A Caucasian man, ideally, would be set to zone 6 (mid-grey + 1 stop), an African to zone 4 and an Asian to zone 5. These are their ‘real world’ values but can also be manipulated for creative results. Placing an older woman one zone higher will add more luminosity, fewer shadows and less wrinkles.

Consider a scene in the Arctic: 80% of the scene is white with little else except dark shadows. Were you to set the ‘proper’ exposure (using centre-weighted or balanced metering) by setting the middle grey point (or luminosity slider) to the centre of the scale, the resulting photo would have most of the scene displaying blue or grey. Why? You have told the camera that some of the whites are the middle of the scale making the entire dynamic range shift downwards.

The reason is quite simple: the camera has been programmed around a normal curve, meaning that given any scene the bulk of data will fall within one stop of Middle Grey. In many scenes, this is correct if we assume that the intent is to balance everything in the scene and I don’t mind that the photo looks like everyone else’s.

What if I want to show the nuances of tonality in a glacier. I don’t care about the sky and the only shadows that matter are the ones that give the ice depth and detail. Obviously, I can zoom in to cut out all else and then the camera’s defaults will work fairly well. But my editor always wants a sense of place, so I need to include the whole scene AND want the viewer to be mesmerised by the patterns in the ice.

Then, I need the zone method. Here is a quick example,

  1. I would choose items in the scene to represent the outer limits of luminosity (items I must retain the detailed information)
  2. With this, I have my range (let’s say 7 stops)
  3. Now I must make a choice: what is important subtlety or impact
     — if I want subtlety, then an fstop of 11+ (more likely 22) is recommended
     — if I want impact, then an fstop of 3.5 may be recommended.
  4. Once I have set me aperture, I check to ensure that my outer limits are within the detail dynamic range. If they are not, I can change the aperture to include them (if possible).
  5. Spot meter my subject and place it in its appropriate zone using the shutter speed(more on this later).
  6. Divide the range chosen in step 2 by half. This gives me the limits I had chosen earlier. Check to ensure they are within the dynamic range set (3.5 stops above and below my subject metering).
  7. Take the shot.

end part 1.

Originally published at MJA.